Method and apparatus for controlling the thickness and uniformity of a liquid coating on wire



H. BEE DY 7 METHOD AND APPARATUS FOR CONTROLLING THE THICKNESS March 11, 1952 AND UNIFORMITY OF A LIQUID COATING ON WIRE Filed July 19,

A TTHIM/EV IVEA/TOA SOURCE OF HIGH VOLTAGE Patented Mar. 11, 1952 UNITED- S'TATES PATENT FICE METHOD. AND. APPARATUS .FOR, CONTROL-- LINGZTHE THICKNESS. AND UNIFORMITY OE ALIQUID COATING.ON WIRE Harold-zBeedy; ,Western Springs; Ill.', assignor. to Western rElectriceGompany, Incorporated, New York,. N..,Y,., alcorporation of New York Application J 1113* 19, 1947, Serial No. 762,080

8, Claims... 01.2117e-913I) This vinvention; relates to methods and? appar- ,ratus for controlling the thickness and uniformity of a coating on abasexand more particularly to methodsyand. apparatussforz controlling the. thickness anduniformity of enamel onwire; 5 maintaining. the coating uniform issimplifiedzby When wire" is coated .by'continuously feeding passing'the wire:through a helical, de-tearing the wire through an enamel bath" andthen electrode-2| whichiis;maintained-taterpotential throughtaadiying orttbakingcch'amber;attconstant difference of several thousand volts from thatzof speed. the production: of': a.:. smooth: uniform the wire In by means "of 'a' 'suitable source of high enamelcoatingmf-therdesired"thicknesapresents voltage =221preferably ofdirect current, the-mega.- a difficult: problem; In; passing; through; the tive side ofwhichismnnected to the-helix' and enamel: bath: the wires picks: up excess enamel the positive sideccnnected to :the wirer'l O'E'through thusfo'rming droplets; and :tearse: along the 1 wire, the pu y l3 and 20 w ch may also be oun e the amount ofcexcesscbeing; dependentqupon the The :apparatus willioperate with the polarityr reviscosity of the: enamel, the IIlOlGgiViSCOllS the se t at W positive 'Side connected greater. excess; to the helix: In practice it was found: that :the Objects of this inventioniarettoaprovidetnewand corona-:p is r u y n e n r efiicient, methods, and apparatus for removing tive side.ofthexpowerrsupply-tothe helix: The excess liquid coating from a wire, helix 2| is'more efiicient ifxitisformed froima In accordance with one embodiment of this conductor-havingzm cross section quitera=bit invention, wireis-passed through a n lb th largerx-than that of =the -;wire-'being:enameleda. A and then passed through a helix along the'longiresistor 23 may be connected:in,..series: with the tudinal axis. ofthe helix, the ,helix being at an p w i up y liminth u ni as f a electricarpotentialseveral thousand volts above us y a fiaS -(Werr' thatofthe wire being enameled. As the-freshly 25 As thewire liltpassesrthrougli the-helical;;e1ec1- coated wire passes throughthe helix the excess trode 2| theahigh potential difierence'abetween enamel is-stripped from the wire=by electrostatic the'helix and the wire ill will cause the 818013330? forcesdue to thepotential difference: From static: forces set-up: therebetweentopull the-exthere the wire. ispassedlthrough baking ovens. .to cess of the. freshly applied enamel from" the curetheenamel... wire lmandthe stripping efiectfls'made-iuniform A complete understandingof the -invention will dueto the spiral path' of: theselectrostatic: forces be had by reference to the following detailed dethrough which the wire is being drawn. Because scription' taken inconjunction with the accomof "the-helical shape. of the= de-atearingselectrode, panying single figure drawing-which is -adiathe electrostatic forces \move'aaroundzthezlwire grammatic illustration of one embodiment of the 5 as it progresses and do not tend to pull the mainvention herein. terial which remains on the wire to one side as In order to practice the invention, enamel may would be the case if a plane were used as a debe applied to a wire Ill by any suitable method, tearing electrode. for example, as shown in the drawing the wire I!) The thickness of the enamel coating may be may be taken from a supply spool II and dipped 40 controlled by controlling the voltage on the deinto an enamel bath I2 by passing the wire tearing electrode 2|. After the wire has passed I0 around a metal pulley l3 submerged in the through the electrified helix it may be passed enamel bath which may be contained in any suitthrough a suitable oven 24 to bake and cure the able tank M. The wire I0 is pulled through the enamel coating. enamel bath by rotative power applied to a take- 5 The dimensions of the helical electrode 2|, inupreel l 5 to which the end of the wire has been eluding its diameter, the pitch of the spiral turns. attached after threading it around the pulley l3 and the size of the conductor of which it is formed and another metal pulley 20, the wire being held together with the amount of voltage applied beunder reasonable tension at all times. tween the helix and the wire II] are dependent In accordance with old practices in the art the upon the viscosity of the enamel bath and the wire 10 as it emerged from the enamel bath linear speed of the moving wire in order to obtain would pass through a drying oven to cure the a desired uniformity and thickness of coating. enamel without any attempt to remove the excess Such factors may be correlated to obtain the deenamel or to maintain the coating on the wire sired result and may be arrived at by experiment. uniform. Other practices in the art include the 5 The diameter, pitch and length of the helix would be determined experimentally for any given application. In general, a material of high viscosity requires a higher voltage to remove the excess material than material of low viscosity and would require a larger diameter helix to avoid electrical breakdown. It might also require a somewhat longer helix to assure complete removal of tears or droplets. The length of the spiral and its pitch will also be largely dependent upon the speed of movement of the wire.

Because of the efiicient de-tearing and stripping action of the invention herein, enamels of relatively high viscosity may be used without the necessity of mechanical stripping dies and a smooth coat of enamel may be applied with fewer passes than is possible under older practices by making possible the use of more viscous enamel. The apparatus herein is very simple, it is nonclogging and will pass splices and welds in the wire which could not go through mechanical dies.

What is claimed is:

1. A method of removing excess liquid enamel from a wire being enameled comprising subjecting said wire to a corkscrew-shaped spiral electrostatic field and moving the wire through said field in line with the major axis of said spiral field.

2. In a method of enamelling wire, the step of removing excessive liquid enamel from said wire by passing said wire through an open helical electrostatic field in line with the major axis of said field.

3. A method of controlling the thickness and uniformity of a liquid coating on a wire comprising applying a liquid coating on a wire, and stripping excess coating from the wire by passing the wire through a helically shaped electrostatic field in line with the major axis of said helical field, the adjacent turns of the helix being spaced apart sufliciently to create unbalanced forces on the portion of the wire in said field.

'4. A method of controlling the thickness and uniformity of enamel coating on wire comprising applying a liquid coating of enamel to said wire, establishing a field of electrostatic forces spiralling openly along and around said wire, imparting relative movement axially of the wire between the wire and the spiral field of electrostatic force to strip the excess liquid from said wire, and drying the enamel remaining on the wire.

5. An apparatus for stripping the excess of a liquid coating from wire comprising an open helical electrode, means for drawing said liquid coated wire through said helical electrode along the longitudinal axis thereof, and means connected to said helical electrode and adapted to be connected to said wire for establishing a potential difference between said helical electrode and said Wire to strip the excess liquid coating from said wire by electrostatic force.

6. An apparatus for coating wire with enamel comprising means for applying liquid enamel to a wire, means for moving said wire longitudinally, and means for setting up an electrostatic force extending spirally around and along said moving wire to strip the excess enamel from said wire; the last said means comprising an open helical electrode and a source of relatively high voltage connected to said electrode and said wire.

7. An apparatus for controlling the thickness and uniformity of an enamel coating comprising a helical electrode through which a wire having a coating of liquid enamel may be passed coaxially, the adjacent turns of said helix being spaced substantially apart and a source of voltage coupled to said electrode and to said wire, said voltage being of such value as to set up electrostatic forces strong enough to strip the excessive enamel from the wire.

8. A method of controlling the thickness and uniformity of enamel coating on a wire, which comprises applying a coating of liquid enamel on a wire, creating a helically shaped electrostatic field having substantial spaces between adjacent turns of the helix, advancing the wire through the helically shaped electrostatic field in line with the major axis of the helical field to strip the excess enamel from said Wire by electrostatic force, and then baking the enamel. I

HAROLD BEEDY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 253,227 Rice Feb. '7, 1882 1,688,854 Daumann Oct. 23, 1928 2,345,390 Flynn Mar. 28, 1944 2,359,476 Gravley Oct. 3, 1944 2,417,798 Ransburg Mar. 18, 1947 OTHER REFERENCES Websters New International Dictionary, 2nd ed. unabridged, page 2428. 

